This invention relates to apparatus for indicating the position of a member and in particular to apparatus in which a code is carried by the member and is read by some form of detecting means as the member moves to give an indication of its position at any one time.
In a conventional position encoder there are a number (n) of tracks extending on the member in its direction of movement and these tracks are read at respective read points. The simultaneous outputs from all the read heads define a digital word indicating the position of the member.
A problem associated with such position encoders is the difficulty in fitting a large number of read points in the available space and the expense arising from the need for the large number of read heads and associated circuitry.